Catalytic olefin isomerization process



United States Patent O 3,409,702 CATALYTIC OLEFIN ISOMERIZATION PROCESS Larry Plonsker, Troy, and John M. McEuen, Ann Arbor, Mich., assignors to Ethyl Corporation, New York, N.Y., a corporation of Virginia No Drawing. Continuation-impart of application Ser. No. 422,520, Dec. 31, 1964. This application Sept. 21, 1967, Ser. No. 669,369

2 Claims. (Cl. 260683.2)

ABSTRACT OF THE DISCLOSURE A process is described for isomerizing a-olefins to olefins using, as the catalyst, mixtures of Group VIII metals on an inert support. The isomerization is carried out at elevated temperatures; a-olefins having from 4 to 24 carbon atoms are effectively isomerized. Useful Group VIII metals are rhodium, palladium, ruthenium and platinum; charcoal is an example of a useful carrier.

CROSS REFERENCES TO' RELATED APPLICATIONS This application is a continuation-in-part of co-pending application Ser. No. 422,520, filed Dec. 31, 1964, now US. 3,352,938, issued Nov. 14, 1967.

BACKGROUND OF THE INVENTION Various processes for isomerizing terminal olefins to internal olefins are known in the art. However, in general, the prior art processes suffer from one or more limitations such as excessive olefin cracking, undesirable olefin polymerization, excessive randomization, or unfavorable economics. It is known that palladium and platinum halides in combination with other ingredients can be employed as isomerization catalysts. US. Patent No. 2,960,550, Nov. 15, 1960, teaches the isomerization of olefins with a catalytic medium consisting essentially of a halogenated, straight-chain, organic acid solution of a halogen-containing salt of palladium or platinum. US. 2,960,551, Nov. 15, 1960, teaches similar catalytic media which consist essentially of a phosphorus oxychloride solution of a halogen-containing palladium or platinum salt. In contrast, this invention comprises the discovery that halide salts of palladium and platinum are unnecessary and that the isomerization of terminal olefins to internal olefins can take place in the presence of a mixture of Group VIII metals in elemental for-m. Furthermore, this invention comprises the discovery that halogenated reaction media such as halogenated straightchain organic acids or phosphorus oxychloride are unnecessary in the isomerization of terminal olefins.

SUMMARY OF THE INVENTION A process for isomerizing a-olefins having from 4 to 24 carbon atoms to the corresponding fl-olefins by contacting said a-olefins at elevated temperatures with a catalyst which comprises a mixture of ruthenium, palladium, rhodium or platinum on charcoal as a carrier.

DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of this invention is a process for the isomerization of an olefin which comprises contacting said terminal olefin with a synergistic mixture of Group VIII metals supported on an inert matrix. In a preferred embodiment, a straight-chain terminal olefin having from 4 to 24 carbon atoms is isomerized to a straight-chain internal olefin when the catalyst is selected from such synergistic mixtures as ruthenium-palladium, rutheniumplatinum, ruthenium-rhodium, platinum-palladium, plat- "ice inum-rhodium, palladium-rhodium, ruthenium-platinumpalladium, rutheniumplatinum-rhodium, and platinumpalladium-rhodium supported on an inert matrix. The preferred mixtures of metals employed in the catalyst are ruthenium-palladium, rhodium-palladium, rhodiumruthenium, ruthenium-platinum and ruthenium-rhodiumpalladium.

The above listed mixtures of metals exhibit a synergistic effect in catalyzing olefin isomerization. These mixed metal containing catalysts show unexpectedly greater activity and selectivity than catalysts containing single metals. Thus, by employing catalysts containing mixed metals, a higher conversion of olefin-1 to olefin-2 is obtained while the conversion to other undesirable internal olefins and to paraifins is kept to a minimum.

The :process of this invention is advantageously employed in the conversion of straight-chain terminal olefins having from 12 to about 24 carbon atoms to the corresponding straight-chain internal olefins. However, the process can be employed to isomerize lower olefins such as butene-l, pentene-l, heptene-l, octene-l, nonene-l, and the like. A particular feature of this invention is the high yield of ,B-olefin afforded by the process.

The reaction temperature is not critical, and conversions may be carried out at ambient temperatures or higher. However, in some instances the isomerization rate is too slow for practical use when the process is carried out at a temperature below about C. Thus, the process is generally carried out at least at C. and preferably at temperatures between about 150 C. and the decomposition temperature of the terminal olefin. A highly preferred reaction temperature is from about 150 to about 225 C. Higher tempertaures, however, may also be employed with satisfactory results. Thus, higher olefins, such as dodecene-l, tetra-decene-l, and hexadecene-l, may be isomerized at the reflux temperature of the system which is higher than 225 C.

Atomspheric pressure, or higher or lower pressures, can be employed. Atmospheric pres-sure is especially useful in the isomerization of olefins having from 12 to about 24 carbon atoms. In general, a preferred pressure range is from about 1 to about 20 atmospheres; a most preferred range being from 1 to about 5 atmospheres.

The reaction time is not a truly independent variable but is dependent at least to some extent on the other process conditions employed. In general, higher temperatures usually result in a decrease of reaction time. The reaction time is governed at least to some extent by the degree of isomerization desired. Furthermore, the reaction time depends on the amount of the catalyst used for a given volume of an olefin and on the specific metal catalyst mixture employed since some mixtures are more active than others. When carrying out the process as a batch operation, reaction times of from about 10 minutes to about 40 hours are usually sufficient.

As mentioned above, two or more metals, preferably in a finely divided state supported on an inert matrix, are employed as a catalyst in the process of this invention. Preferably, the supports are in finely divided form or in small states of aggregation such as pellets or tablets having a surface of sufficient area to give an effective catalytic surface. Any inert catalytic support known in the catalytic art can be employed. Preferably, the support is selected from the class consisting of charcoal, alumina, diatomaceous earth, bentonite, firebrick, kaolin, ground glass, silicon carbide, silicon dioxide, kieselguhr, and zeolites. The zeolites are a group hydrated aluminum and calcium or sodium silicates capable of reaction in solution by double decomposition with salts of the alkali and alkaline earth metals. They are of the general type N320 2Al203 3 and CaO-2Al O 5SiO Charcoal, and particularly finely divided charcoal, is the most highly preferred inert support.

The catalyst preferably consists of from one to about weight percent of finely divided metals dispersed on an inert support of about 90 to about 99 weight percent. It should be noted that both the metals and the inert supports can be in other states of aggregation such as pellets or tablets; but finely subdivided material is preferred because it provides larger surface area and thus increases the efficiency of the catalyst. When a catalyst is too active, however, it might be preferable to employ the metals and/or the inert material that is in larger particle size.

The amount of catalyst employed in this process is not critical. However, it is preferred that an amount of catalyst be used which affords a reasonable amount of isomerization in a reasonable reaction time. In general, when the process of this invention is carried out as a batch operation, from about 0.01 to about 40 weight percent of a catalyst consisting of a metal mixture and an inert support is employed. A preferred range is from about one to about weight percent. Thus, for example, if 100 grams of olefin is charged to the reaction vessel, it is highly preferred that from about one to about 15 grams of a catalyst mixture, that is, a mixture of the metals and the inert support, be admixed therewith.

The process of this invention can be carried out as a batch process or as a continuous operation. In a continuous process, an olefin, either in vapor or in liquid phase, may be contacted with the catalyst, but for ractical reasons, liquid phase operations are preferred. When carrying out the process of this invention as a batch operation, it is preferred that a liquid phase be present. Thus, dodecene-l can be isomerized by refluxing a mixture of dodecene-l and a catalyst at atmospheric pressure. Similarly, butene-l can be isomerized in a batch operation by contacting it with a catalyst at a pressure under which the terminal olefin is a liquid. Alternatively, butene-l (or any terminal olefin that is gaseous at the reaction temperature) can be isomerized according to the process of this invention by bubbling the gaseous olefin through a liquid reaction mediumin contact with the catalyst.

A very important feature of this invention is the fact that the catalyst employed in this process may be re-used for subsequent isomerizations and, thus, improve the economics of the process. When the process of this invention is carried out as a batch operation, the catalyst may lose some activity after about five runs, however.

Although this process can be conducted in the presence of a solvent, we prefer not to employ a solvent when isomerizing an alpha olefin which is in the liquid state under the reaction conditions employed.

Those solvents which may be employed should be inert under the reaction conditions. Non-aqueous materials such as the saturated hydrocarbons, e.g., pentane, hexane, isopentane, dodecane, and the like are preferred, but ethers, alcohols, and halogenated hydrocarbons may also be used.

The processes of this invention may be carried out either in air or in an inert atmosphere. When an inert atmosphere is desired, nitrogen is preferred, mainly for economical reasons. However, other inert gases may be used with equal success. When this invention is carried out as a continuous process, an inert gas, preferably nitrogen, is advantageously used as a carrier for the olefin that is being passed through the catalyst bed. In such a process, the amount of nitrogen used is measured by cubic centimeters (cc.), passed through the reaction tube per minute. It is preferred that the nitrogen flow be such that the ratio of the volume of nitrogen to the volume of olefin be from 1:1 to 1000:1.

When the process of this invention is a continuous process, an additional variable of space velocity is introduced. Space velocity may be defined by the following relationship ml. olefin injected/m1. catalyst hours The above formula for calculating space velocity holds whether the olefin employed is in liquid or gas phase. The value for space velocity, however, will be substantially different when the olefin is in one or the other physical state. For example, when the olefin is in a liquid state, space velocity generally is in the range of from 0.1 to about 100, and more preferably, from 0.5 to about 10. On the other hand, when the olefin is in a gaseous state, space velocity is in the range of from about 50 to about 500. The reason for the difference in the values for space velocity is that there is substantially much less olefin in each milliliter of olefin in gaseous state than in each milliliter of olefin in a liquid state.

Space velocity is thus a measure of the speed with which an olefin is passed through the reaction tube containing the catalyst bed. Space velocity in a continuous process, similarly as the reaction time in a batch process, is not a directly independent variable. It depends on the reaction temperature, the activity of a particular catalyst employed, and the degree of isomerization desired. It will be seen then that in order to achieve a given amount of isomerization, the space velocity generally will be different for different catalysts even if all other variables remain constant.

From the above discussion, it is clear that the space velocity and the nitrogen flow must be determined for every isomerization when a different catalyst or a different olefin is employed. Not only the activity of the catalyst and the reaction temperature must be considered, but also the degree of isomerization desired, since, generally, the higher the degree of isomerization, the more time is required to attain it. Generally speaking, however, space velocity for liquid olefins will be in the range of from 0.1 to about 100, and preferably from 0.5 to about 10, and for gaseous olefins from about 50 to about 500. In Example 26, where 1% ruthenium and 9% palladium was employed as the mixture of metals, said mixing being dispersed on powdered charcoal, space velocity of 1.5 was used. The rate of the nitrogen flow often will have a great effect on the degree of isomerization, as indicated by Examples 26 and 27.

In a continuous process, occasionally a single pass of an olefin through the reaction column might not yield the desired degree of isomerization. In such cases, the partially isomerized olefin may be recycled in the same manner as the fresh olefin through the reaction column to produce the desired degree of isomerization.

The products of this invention can be separated from the reaction mixture by any method known in the art. Suitable separation techniques include filtration, distillation, decantation, chromatography, and the like.

The following examples serve to illustrate this invention, but do not limit it. All parts are 'by weight unless otherwise indicated.

EXPERIMENTAL Example l.Batch isomerization A flask equipped with a side arm fitted with a diaphragm was charged with 18 parts of dodecene-l and 2 parts of a catalyst consisting of 9 wt. percent of 5% palladium on charcoal and 1 wt. percent of 5% ruthenium on charcoal. The flask was swept with nitrogen and the reaction mixture was heated to reflux for 8 hours while Space velocity (s.v.)

stirring. The reaction mixture was then filtered to rea commercial operation since it is often difficult to stop move the catalyst and the isomerized olefin was deterthe reaction at the most ideal time. The above noted mined by infrared and vapor phase chromatography advantages of the catalysts of this invention are illusanalysis to contain 79% dodecene-2. trated by the following examples.

ISOME RIZATION OF DODECENE-l Wt. Percent Times, Paraf., l-olefin, 2-olefin, Internal Catalyst 01 Catalyst Temp. hrs. Percent Percent Percent olefins,

Percent 5% Ru/C 1 Reflux 0.25 0. 6 4. 1 69.4 25. 90 5g, 10 d 6 4.2 10.1 73.2 12.5 u do 8 a. 1 8.6 79.2 9.1

Examples 2-26 are contained in Table 1 and in all of As may be seen, ruthenium on charcoal is very active these examples the procedure described in Example 1 was since in only 15 minutes, the isomerizati'on yields a large followed changing only the catalysts used and their amount of internal olefins, although paraflin content and amounts, the temperature, and the reaction time as inunisomerized l-olefin are desirably low. Although, as dicated in the table. indicated by the above date, palladium on charcoal gives In the following table, percent Ru/ C indicates percent much better results than ruthenium, the amount of paraf- -ruthenium (or another metal as indicated) dispersed on fin, unisomerized l-olefin, and internal olefins is somecharcoal. In all the examples in the table, the catalyst in what high. The mixture of ruthenium on charcoal and column 3 used in the amounts specified in column 5 were palladium on charcoal, however, produces the highest 5% by weight of indicated mixture of metals dispersed percentage of the 2-olefin and, at the same time, the on powdered charcoal. lowest percentage of undesirable internal olefins and TABLE 1 Example Catalyst Composition Wt. Ratio of Weight Temper- Time, Product and Percent Number Olefin Percent M|/C:Wt. Percent MJC MetalnMetalz Percent ature Hrs. 2-olefin in the Final Catalyst Product 2.. Dodecene-l 0.5% Ru/C:5% Pd/C 1:10 5.5 22 D0decene-2 (77%). do 1% Ru/C:5% Pd/C 1:5 6 4 D0decene-2 (76%). 1:9 10 8 Dodecene-2 (81%). 1:1 10 1 Dodecene-2 1:7.5 8.5 8 Dodecene-2 (76%). 1:9 10 1 Dodecene-2 (73%). 1:9 10 3 Dodecene-2 (83%). 1:1 5 8 Dodecene-2 (62%). 1:1 5 2 Dodecene-2 (71%). 1:1 1 8 Dodecene-2 (69%). 1:4 10 8 Dodecene-2 (62%). 3:7 10 7 Dodecene-2 (56%). 1:1 10 4 Dodecene-2 (68%). 10 1 Dodecene-Z (80%).

3:1 10 10 Tetradecene-2. 3:1 10 10 Hexadecene-2. 1:100 5 2 Hexene-2. 1:50 10 8 0. 3:7 10 20 Tetraeicosene-2. 1:1 10 12 Eicosene-2. 1:1 10 10 Octadecene-2. Decene-1 1:1 10 4 Decene-Z. 24--. 5methyldodeeene-1 .t. 1% Ru/C:5% Pd/C. 1:5 6 Reflux 4 5-methyldodecene-2- 25 2-methyldodecene-1 5% Ru/C:5% Pd/C--- 1:1 10 .d0 1 2-methyldodecene-2.

Examples 1, 6, 9, 11, 15 and 16 were repeated following the same procedure except that the metal con- 50 strikes ahap-py medium between ruthenium and palladium tent of the catalyst was changed from 5% metal on with respect to the amount of paraffins and unisomerized charcoal to 0.1%, 1%, 10%, 15% and 20% of a metal l-olefins in the product. An even more striking example on charcoal. Results comparable to those in Table 1 were of synergistic elfect is shown when rhodium and palladiobtained. um are employed.

ISOMERIZATION OF DODECENE-l Wt. Percent Times, Paraf., l-olefin, 2-olefin, Internal Catalyst of Catalyst Temp. hrs. Percent Percent Percent olefins, Percent As stated above, the mixed metal catalysts of this invention exhibit synergistic effect in the olefin isomeriza- Here, although rhodium requires a comparatively long tion reactions. The synergism is exhibited primarily by time for isomerizing l-olefin to 2-olefin and palladium improving the ability to control the reaction; that is, gives rather high amounts of l-olefin and internal olefins by minimizing the formation of undesirable products in the product, the mixture of rhodium on charcoal and such as parafiins and internal olefins, and improving the palladium on charcoal yields a strikingly high percentage conversion of l-olefin to the desired 2-olefin. At the of 2-olefin and at the same time, low percentages of same time, the activity of the catalyst is controlled so that paraffin, l-olefin and internal olefins.

any additional contact between the isomerized olefin Another synergistically active combination of catalyst and the catalyst will not cause the product to isomerize metals is the combination of ruthenium and rhodium.

further to internal olefins. This is of utmost importance in The data in the following examples illustrates this effect.

lSOMERIZATION OF DODECENE-l Wt. Percent Times, Paratfin, l-olefin, 2-olefin, Internal Catalyst of Catalyst Temp. hrs. Percent Percent Percent olefins,

Percent Ru/C 0.5 Reflux 8 1.2 80 18.2 0.6 5% Rh/C 1 150 s 0.5 71 21.5 1.0

5 Reflux. 2 1. 0 70. 6 18. 4

The data above shows that when ruthenium or rhodium were regulated by a temperature regulating means such on carbon are used alone to isomerize dodecene-l to as a Gardsman Controller. Part of the tube was packed dodecene-Z, the yield of dodecene-2 is only about 20 with the catalyst consisting of a powdered charcoal conpercent. When a mixture of rhodium and ruthenium on taining 1% ruthenium and 9% palladium. Below and carbon black is used, the yield of dodecene-Z is triple. above the catalyst were placed glass beads to facilitate Thus, using the rhodium-ruthenium catalyst system, the better mixing of the olefin with the catalyst. yield of dodecene-Z obtained is about 70 percent in each The average temperature in the pre-heat area was case. about 192 C. and the average temperature in the center This synergistic interaction is also evidenced by the of the catalyst bed was about 193 C. About 31 parts combination of ruthenium and platinum on carbon black. of dodecene-l were injected into the column by 21 Con- The data which follows illustrates this unexpected effect. tinuously Variable Syringe Pump at a space velocity of ISOMERIZATION OF DODECENE-l Wt. Percent Times, Paraifin, l-olefin, 2-olefin, Internal of Catalyst Temp. hrs. Percent Percent Percent olefins,

Percent 0. 5 Reflux. s 1. 2 s0 18. 2 0. 0 10 ..d0 7 1.2 61.2 30.5 7.0

10 s 1. e 20 01. s 10. 0

The data clearly shows that only 18 percent of dodecene- 1.5 and a nitrogen flow of about 100 cc./minute, meas- 1 is isomerized to dodecene-Z when ruthenium on carbon ured by a Manometer Flow Meter. The isomerized black is used as a catalyst; the yield of dodecene-Z from dodecene-l was condensed in a receiver, cooled in an dodecene-l when using platinum on carbon black as ice bath. The product contained 45.8% dodecene-2 (75% the catalyst is only 31 percent. However, when a combinayield, 63% conversion). tion of ruthenium and platinum on carbon black is used Example 27 as a catalyst, the yield of dodecene-2 from dodecene-l is increased to between and 68 percent. This certainly mple 26 was repeated changing only the pre-heat is unexpected from the data obtained for ruthenium or 5 temperature from 192 C. to 204 C. and the nitrogen platinum alone. flow from 100 cc./minute to 10 cc./minute. The product This synergistic interaction also occurs with the ternary contained 63% dodecene-2 (72% yield, 88% conversion). system comprising ruthenium, rhodium and palladium. Examples 26 and 27 were repeated using other olefins The data presented below illustrates this synergy. such as decene-l, tetradecene-l, and hexadecene-l and ISOMERIZAIION OF DODEOENE-l Wt. Percent Times, Paraffin, l-olefin, 2-olefin, Internal Catalyst 0! Catalyst Temp. hrs. Percent Percent Percent olefins,

Percent 5% Ru/C 0.5 Refiuxnu 8 1.2 80 18.2 0.6 10 do 6 4 2 10.1 73.2 12.5

10 Reflux 1 1. 5 8. O 79. 6 10. 9

As the above data clearly shows, the percent dodecenecatalysts such as rhodium-palladium, rhodium-ruthenium, 2 obtained from the isomerization of dodecene-l using ruthenium-palladium and ruthenium-rhodium-palladium the ruthenium, rhodium, palladium ternary catalyst syssupported on charcoal, powdered and pelleted, alumina tem is higher than the percent dodecene-2 obtained for and silicia on alumina. In these isomerizations, results any of the individual catalyst components themselves. comparable to those in Examples 26 and 27 were obtained. Example 26.Continuous isomerization The internal olefins produced by the process of this I invention are well known compounds and have the many The lsomerllatlon y a continuous "P was Carried utilities which are known for them. For example, they Out In a tube q pp Wlth thermocouples and two heat 70 are valuable chemical intermediates and can be transers. The th m P wefefor the l i of measformed into acids by an ozonolysis reaction. Thus, for 1111112 the temperature at Varlous locauohs 1n the tube example, tetradecene-2 can be reacted with ozone to yield d th t heaters were arranged in such a manner that lauric acid, a detergent range acid. Similarly, the other inone served as a pro-heater and the other as a main heater ternal olefins produced by this process can be ozonized to located in the area of the catalyst bed. The temperatures yield the corresponding acids. When ozonizing the products of the process of this invention, the reaction is generally carried out at a low temperature; e.g., from 50 to about 10 C. After the ozonization reaction is completed, the resultant reaction mixture is usually treated with another oxident such as air or oxygen to obtain the product acid. The secondary oxidation is usually carried out at a temperature within the range of 20 to 90 C. Solvents which can be employed in the ozonolysis of olefins include inert sol-vents such as chloroform and carbon tetrachloride or hydroxylic solvents such as methanol and acetic acid.

Having fully described the process of this invention, the products produced thereby and their many utilities, it is desired that this invention be limited only by the lawful scope of the appended claims.

We claim:

1. A process for the preparation of straight-chain fl-olefin having 4 to about 24 carbon atoms from the corresponding straight chain a-olefin, said process comprising contacting said a-olefin with about 10* weight percent of an isomerization catalyst containing about 5 weight per cent of a ruthenium-platinum mixture, said mixture consisting substantially of 1 part ruthenium and from 1 to 4 parts of platinum dispersed on a finely divided activated charocoal, said process being carried out at atmospheric pressure in an inert atmosphere at about the reflux temperature of the system.

2. The process of claim 1 wherein said ,B-olefin is dodecene-2 and said oi-olefin is dodecene-l.

References Cited UNITED STATES PATENTS 3,180,097 5/1965 Brennan et a1. 260-68365 3,205,282 9/1965 Sparke et a1. 260-6832 3,214,487 10/1965 Mattox 260-6832 3,248,448 4/1966 Goble et a1. 260-6832 3,248,450 4/1966 Goble 260-6832 FOREIGN PATENTS 448,177 4/1948 Canada.

DELBERT E. GANTZ, Primary Examiner.

V. OKEEFE, Assistant Examiner. 

